Golf ball surface designs have changed over the years as better materials, better land and dimple designs and better sighting indicia have evolved. However, a study of the art indicates that there are no theoretical or empirical theories which lead to the "best" designs for one or more purposes as the following discussion shows. A major design trend has been toward a maximum of dimple area and a minimum of land area. This trend finds it epitome in the Excalibur ELT/Tour model marketed by Excalibur Golf Co. of Farmington Hills, Mich. This ball has dimples of different diameters and, effectively, no lands. U.S. Pat. No. 5,033,750 to Hisashi Yamagishi teaches the use of dimples of three different depths.
U.S. Pat. No. 4,722,529 to Michael Shaw et al, however, teach an improved average flight distance with a ball having at least 30 dumb bell shaped bald spots or "lands" arranged on the ball surface so as to form dodecahedrons.
Another trend is to provide indicia for the desired direction of roll. This design trend is exemplified by U.S. Pat. No. 676,506 to R. D. Knight et al who applied lines to the ball surface and U.S. Pat. No. 4,258,921 to J. C. Worst who puts an "undimpled" patch 90.degree.-100.degree. from the center of the imprint of the brand name. Still another approach is to place an inverted "T" on the ball surface at the sweet spot. When putting, the club is aligned with the bar of the "T" and, when driving, the base is aligned with the drive direction (Brookstone collection, Spring 1994, p. 19).
Still another trend is to place dimples so as to form lands along geometrically positioned patches of dimples. The following patents exemplify various approaches.
U.S. Pat. No. 4,142,727 to Michael Shaw et al teaches a ball having a surface dimple pattern which provides at least 12 symmetrically disposed rectangular bald patches. U.S. Pat. No. 3,819,190 to D. A. Nepela et al teaches a design with two bald poles and a dimpled equator. U.S. Pat. No. 4,762,326 to William Gobush teaches a pattern design with seven great circles which, in truncated octahedron form, form six squares each of which breaks down into four equal isosceles triangles. U.S. Pat. No. 5,046,742 to G. T. Mackey teaches a "soccer" ball design of hexagons and pentagons and uses dimples of differing sizes to form lands of different sizes. U.S. Pat. No. 5,078,402 to Kengo Oka teaches a cuboctahedron design of triangles and squares with uneven dimpling which forms lands of varying sizes. U.S. Pat. No. 5,252,132 to Kengo Oka teaches a ball with 40 or more rectangular lands. U.S. Pat. No. 4,787,638 to Masashi Kobayashi teaches balls having lands and dimples which are covered with even smaller dimples.
While these and other references address different land and dimple golf ball designs, professionals and duffers alike continue to miss softly-tapped putts from short distances. It appears from a study of the problem of erratic rolls from softly tapped putts, that the dimples interaction with the putter surface and/or the grass of the green is greater with slow moving putts than with faster moving putts.
In hard impact golf shots such as long putts, driving and iron play, the impact of the club on the ball causes the ball to compress, which in turn flattens an area of the ball surface against the club head. For these harder blows, the irregularities on the surface of the ball caused by dimples have little effect on the initial direction of the ball, since the dimples are flattened. However, for softly tapped putts, the irregular surface pattern caused by dimples can detrimentally affect the initial direction of the ball. If a golf ball is set on a hard surface, it wobbles until it settles flush across a dimple. Depending on the number of dimples, the angular rotation required to move to the next flush dimple position can range between approximately 7 and 12 degrees. The same is true if the putter head taps the ball softly on a land or dimple as the force of the blow is transmitted directly through the center of the ball casing, the ball will travel truly in line with the putter stroke if irregularities in the turf do not skew the ball path.
However, if the putter contacts a dimple off center i.e., partially on a land edge and a dimple, the force of the putting stroke is not transmitted through the center of the ball. This not only sets the ball off at a tangent, but produces a moment about the center of the ball resulting in a small amount of spin. If the point of contact is only 5 degrees offset from a line through the center of the ball in the direction of the putting stroke, then the tangential misdirection alone over a two foot putt calculates to 2.1 inches--enough to miss the cup.
An additional effect on the initial direction of the ball can be caused by the orientation of the dimple at the point of contact with the ground. Due to dimples, the outside shape of the contact area with the turf is generally hexagonal. If this hexagonal area is symmetrical about a line drawn through the center of the dimple in the direction of the intended putt, then the lateral effect of the hexagon on the putt will be zero. If it is asymmetrical, then the hexagon will affect the initial direction, either to the left or right, of the intended direction.
The present invention ameliorates these effects, by ensuring that during the putting stroke, the golfer can align the ball so that a land is in contact with the ground while, simultaneously, a second land can be contacted by the putter head. The sighting of the putt along the line of lands on the rear, top and front center axis of the line of the desired ball roll also ensures that the golfer can better align a putt or a drive.
Depending on the type of projection utilized in portraying a golf ball, and the positioning of the lands, the land design can be portrayed in terms of imaginary great circles alone or as a combination of great circles and complementary great circles, i.e., a great circle which can be drawn on lands formed by other great circles, e.g., the great circle around the surface of the ball as shown in FIG. 1. For the purposes of this invention, complementary great circles are ignored.